Hi,
Am Do., 30. Apr. 2020 um 23:56 Uhr schrieb Guoqing Jiang
<guoqing.ji...@cloud.ionos.com>:
> The logic in attach_page_buffers and __clear_page_buffers are quite
> paired, but
>
> 1. they are located in different files.
>
> 2. attach_page_buffers is implemented in buffer_head.h, so it could be
> used by other files. But __clear_page_buffers is static function in
> buffer.c and other potential users can't call the function, md-bitmap
> even copied the function.
>
> So, introduce the new attach/clear_page_private to replace them. With
> the new pair of function, we will remove the usage of attach_page_buffers
> and __clear_page_buffers in next patches. Thanks for the new names from
> Christoph Hellwig.
>
> Suggested-by: Matthew Wilcox <wi...@infradead.org>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: "Darrick J. Wong" <darrick.w...@oracle.com>
> Cc: William Kucharski <william.kuchar...@oracle.com>
> Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
> Cc: Andreas Gruenbacher <agrue...@redhat.com>
> Cc: Yang Shi <yang....@linux.alibaba.com>
> Cc: Yafang Shao <laoar.s...@gmail.com>
> Cc: Song Liu <s...@kernel.org>
> Cc: linux-r...@vger.kernel.org
> Cc: Chris Mason <c...@fb.com>
> Cc: Josef Bacik <jo...@toxicpanda.com>
> Cc: David Sterba <dste...@suse.com>
> Cc: linux-bt...@vger.kernel.org
> Cc: Alexander Viro <v...@zeniv.linux.org.uk>
> Cc: Jaegeuk Kim <jaeg...@kernel.org>
> Cc: Chao Yu <c...@kernel.org>
> Cc: linux-f2fs-de...@lists.sourceforge.net
> Cc: Christoph Hellwig <h...@infradead.org>
> Cc: linux-...@vger.kernel.org
> Cc: Anton Altaparmakov <an...@tuxera.com>
> Cc: linux-ntfs-...@lists.sourceforge.net
> Cc: Mike Marshall <hub...@omnibond.com>
> Cc: Martin Brandenburg <mar...@omnibond.com>
> Cc: de...@lists.orangefs.org
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Sebastian Andrzej Siewior <bige...@linutronix.de>
> Cc: Roman Gushchin <g...@fb.com>
> Cc: Andreas Dilger <adil...@dilger.ca>
> Signed-off-by: Guoqing Jiang <guoqing.ji...@cloud.ionos.com>
> ---
> RFC -> RFC V2: Address the comments from Christoph Hellwig
> 1. change function names to attach/clear_page_private and add comments.
> 2. change the return type of attach_page_private.
>
> include/linux/pagemap.h | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index a8f7bd8ea1c6..2e515f210b18 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -205,6 +205,41 @@ static inline int page_cache_add_speculative(struct page
> *page, int count)
> return __page_cache_add_speculative(page, count);
> }
>
> +/**
> + * attach_page_private - attach data to page's private field and set
> PG_private.
> + * @page: page to be attached and set flag.
> + * @data: data to attach to page's private field.
> + *
> + * Need to take reference as mm.h said "Setting PG_private should also
> increment
> + * the refcount".
> + */
> +static inline void attach_page_private(struct page *page, void *data)
> +{
> + get_page(page);
> + set_page_private(page, (unsigned long)data);
> + SetPagePrivate(page);
> +}
> +
> +/**
> + * clear_page_private - clear page's private field and PG_private.
> + * @page: page to be cleared.
> + *
> + * The counterpart function of attach_page_private.
> + * Return: private data of page or NULL if page doesn't have private data.
> + */
> +static inline void *clear_page_private(struct page *page)
> +{
> + void *data = (void *)page_private(page);
> +
> + if (!PagePrivate(page))
> + return NULL;
> + ClearPagePrivate(page);
> + set_page_private(page, 0);
> + put_page(page);
> +
> + return data;
> +}
> +
I like this in general, but the name clear_page_private suggests that
this might be the inverse operation of set_page_private, which it is
not. So maybe this can be renamed to detach_page_private to more
clearly indicate that it pairs with attach_page_private?
> #ifdef CONFIG_NUMA
> extern struct page *__page_cache_alloc(gfp_t gfp);
> #else
> --
> 2.17.1
>
Thanks,
Andreas
